What to leave out…File name extension. This is a very common one. "cgi", even ".html" is something which will change. You may not be using HTML for that page in 20 years time, but you might want today's links to it to still be valid. The canonical way of making links to the W3C site doesn't use the extension.

If you set the permalink value to be false, this will disable writing the file to disk in your output folder. The file will still be processed normally (and present in collections) but will not be available in your output directory as a standalone template.